Apparatus and method for determining feedscrew and barrel wear

Abstract

An apparatus and a method for determining wear of a feedscrew and barrel combination includes a measuring aperture formed in a wall of the barrel, a gage plug releasably retained in the measuring aperture and having an inner end curved to correspond to a curvature of a surface of the central bore surrounding an inner end of the measuring aperture, and a retaining plug releasably retained in the measuring aperture for maintaining the gage plug in place. When the plugs are removed, the gage plug can be measured for barrel wear and a probe can be inserted into the measuring aperture for determining feedscrew wear. A test bar simulating feedscrew wear is used to calibrate the probe.

1. A gage plug for determining wear of a barrel for a feedscrew comprising:
 a generally cylindrical body adapted to be releasably retained in a measuring aperture formed in a wall of a barrel having a central bore; 
 a shoulder formed at an inner end of said body; 
 a plug inner section connected to said body inner end and having an inner end curved to correspond to a curvature of a surface of the central bore surrounding an inner end of the measuring aperture; and 
 locating means for maintaining rotational alignment of said plug inner section inner end with the central bore surface during rotation of a feedscrew in the central bore of the barrel when said gage plug is installed in the measuring aperture whereby when the plug gage is releasably retained in the measuring aperture, said plug section curved inner end is aligned at the central bore curved surface. 
 
   
   
     2. The gage plug according to  claim 1  wherein said plug inner section is formed of a material having a wear rate corresponding to a wear rate of the central bore surface. 
   
   
     3. The gage plug according to  claim 1  wherein said plug inner section has a cap at said plug inner section inner end formed of a material having a wear rate corresponding to a wear rate of the central bore surface. 
   
   
     4. The gage plug according to  claim 1  wherein said locating means includes a pin extending from said shoulder. 
   
   
     5. The gage plug according to  claim 1  wherein said locating means includes a slot formed at an outer end of said body and a pin removably received in said slot. 
   
   
     6. The gage plug according to  claim 1  including a plug outer section attached to said body inner end and having a larger diameter than a diameter of said plug inner section, and a plug intermediate section connecting said plug outer section and said plug inner section. 
   
   
     7. The gage plug according to  claim 6  wherein said plug intermediate section tapers from said plug outer section diameter to said plug inner section diameter. 
   
   
     8. The gage plug according to  claim 1  wherein said plug body has an outer end with a tool engaging recess formed therein.